Six months female baby breasts big reason, and fetal period estrogen level, body obesity, breast knot related to the following: 1, the baby in six months when the breast enlargement, the main consideration and the fetus is not born before, the mother’s body hormone level related. In the mother’s body, the mother’s body estrogen levels increase, will enter the baby’s body through the placenta, after the birth of the baby estrogen level interruption, it will lead to breast muscle enzyme increase prone to this situation. Generally will not be too obvious, in the baby about one year old will gradually shrink. 2, some babies in infancy during the upper body is relatively obese, the chest will also hoard too much fat, will lead to the baby’s breasts look bigger, generally do not need to deal with, can be closely observed. 3, if the baby’s body oestrogen levels increase in a one-off increase, will also lead to breast development, this situation does not have to worry too much, but to closely observe, the Never squeeze the baby’s breast, or it may become infected.